The first time you email to a contact list, follow these steps:
Step One: Click People on the bottom ribbon
Step Two: Find the local contact/group/list in the left bar
Step Three: In the right pane, there is a mail icon (an envelope) just below the name on the right hand side. Click that.
Step Four: This will launch an email to the group chosen.
Step Five: On all subsequent mailing uses, just start typing the group's name and it will auto resolve in the email being sent.